English is not my first language, so pardon my errors and stuff.

A01 uses the keyboard's layout as the table. The code consits of two rows or onr line seperated by a dash.
The first row or the first half of the code represents the colum of keys (ex 1=QAZ, 4=RFV) and it's range is around 0 ~ 9.
The second half of the code is the row of which the keys are located(ex 1=QWERTY..., 2=ASDFG..., etc) It's range is around 1 ~ 3.
To decode it get the first number of the first half of the code and the first number of the second half in order to point where the first letter is, then continue afterwards. (ex [1][1]=Q, [4][2]=F)


A02 uses MD5 to encrypt their keys. Each hash corresponds to a single letter. They do that by hashing [letter]+[xxx]+[175]. XXX corresponds to three random numbers ranging to 176~999. I can't figure out if the numbers are random or if they have some significance. At the moment, the only way to crack these is to try out every letter+xxx+175 combination.

A03 is a unique one. You start of with a default key, in which this case is 'aaaa'. You then hash the first letter and the default key with MD5. A new key/cluster is generated by extracting the first four letters of the hash(ex. md5(f+aaa) -> e65a1bfc67e... the new key/cluster would be 'e65a').
The second letter would be then hashed with the first cluster and the first four letter of the output would be then extracted, to be the second key or cluster. Continue your way afterwards until the last letter. In order to decode it, you would need to try out all the letters and symbols with the default key and check if the first 4 letters of the hash would match to the first cluster. Try out the first cluster with the letters and check if it matches the second cluster, and so on.

A04 uses SHA1, if fairly difficult for me to explain but I'll try. In order to create A04 codes, you must first deignate a key, in the early days of A04 they used QR Codes to store the keys for unknown reasons. Then, hash the first two letters with the key, the first half of the hash would correspond to the first cluster, the second two numbers will then be hashed with the key, etc. For every other encryption the last half of the hash will become the cluster. Decrypting A04 is very much the same as A02.

ex. hello
[he][el][ll][lo]
 /\  /\  /\  /\
 ||  ||  ||  || xxxxxxxxxx[ddxxxxxxxx]
 ||  ||  || [ccxxxxxxxx]xxxxxxxxxx
 ||  || xxxxxxxxxx[bbxxxxxxxx]
 || [aaxxxxxxxx]xxxxxxxxxx

Thus the output will be:
aaxxxxxxxx bbxxxxxxxx
ccxxxxxxxx ddxxxxxxxx